<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="button" value="弹出消息框" onclick="alert('helllo world')"/>
    <input type="button" value="yes" onclick="alert (document.write('<h1>hello world!</h1>'))"/>
</body>
</html>